The present invention relates to a method for producing a lens with ultraviolet-curable resin and an apparatus therefor.
2. Description of the Related Art
Methods for producing an aspherical lens, consisting of a glass blank and a resin layer laminated thereon, are already known, as disclosed for example in the Japanese Patent Application Laid-open Nos. 60-56544 and 60-243601.
FIG. 9 illustrates such conventional methods, wherein shown are a glass blank 61; a metal mold 63; an ultraviolet-curable resin layer 62; and ultraviolet light U. Ultraviolet-curable resin for forming the resin layer 62 is placed between the glass blank 61 and the metal mold 63 and is cured by the irradiation of ultraviolet light U, and the metal mold 63 is separated from the resin layer 62 to obtain a lens having the resin layer on the glass blank.
However, in such conventional method, even if the irradiation from the light source is conducted in a uniform and parallel manner, the reflections on the faces of the metal mold and of the glass blank result in nonuniform distribution of light intensity over the lens face as shown in FIGS. 2 and 3, eventually leading to nonuniform curing speed of the ultraviolet-curable resin. As a result, since the curing is completed faster in a portion receiving a high irradiation intensity and slower in a portion receiving a low irradiation intensity, a stress is generated in the cured resin layer to deteriorate the precision of the lens face. Also, since the faster curable portion receiving higher irradiation intensity is cured with absorption of surrounding uncured resin in order to compensate for the contraction of resin resulting from curing, the slower curable portion receiving lower irradiation intensity results in a lack of the amount of resin and shows defects such as shrinkage.